A bit OT, as this is not one of the usual sophisticated repairs posted here.
SWMBO was not happy as the hand-held rechargeable vacuum cleaner was failing to switch on most of the time. It used a simple slide switch, but the motor worked barely once in a dozen attempts.
I dismantled it to find a simple slide switch - in the back "off" position the 10 NiMH batteries were connected to the charging circuit, and slid forward they were instead connected to the motor. A few squirts of WD40 failed to solve the intermittent operation, so I removed the switch to examine it.
And found my Christmas present! I usually find these Chinese imports are made to the cheapest spec possible, and expected to find a single-pole single toggle switch. But no, this was a /double/ pole single toggle switch, and the other pole was unused. So I just soldered a wire bridge across to the unused pole, and the switch now works perfectly again.
But how long that pole will last is another matter...